1. Field of the Invention
The present invention relates a solid-state image pickup apparatus, and more particularly to reducing the power consumption of the solid-state image pickup apparatus.
2. Description of the Prior Art
A camera using a charge coupled device (CCD) image sensor, namely, a digital still camera, comprises in addition to the CCD image sensor, a driver for driving the CCD image sensor and a processor for executing various types of processing on the output of the CCD image sensor, as well as a display for displaying the image screen and a memory for storing image signals as data. This type of digital still camera is often driven by battery so that among the various parts comprising the digital still camera, a component not used constantly is shut down during unused periods to reduce power consumption.
Having a driving voltage that is higher compared to an ordinary semiconductor, the CCD image sensor is provided with a voltage booster circuit to boost the battery voltage and generate a driving voltage for the CCD image sensor. Regarding the driver for driving the CCD sensor with pulses, the same voltage booster circuit is used to generate driving pulses having a sufficient voltage. The voltage booster circuit is configured, for example, so that the power supply voltage is superimposed by a pulse-driven charge pump to yield a desired voltage.
The voltage booster circuit supplying power to the CCD image sensor and the driver determines the frequency of the driving pulses so that a predetermined power can be supplied, and continues the voltage boosting operation during the period of operation of the digital still camera. Namely, during the period in which the digital still camera continues operation, the voltage booster circuit, which is the power supply for the CCD image sensor and the driver, continues to operate to keep the CCD image sensor operating. Continuing the operation of the voltage booster circuit, which requires high frequency driving pulses, causes the power consumption to increase.